The tert‐Amino Effect in Heterocyclic Chemistry: Synthesis of Spiroheterocycles

Abstract

Abstract:The tert-amino reaction effect was examined. A new method to synthesize spiro heterocycles is presented. It was shown that the "tert-amino effect" could be applied to the formation of spiro-fused heterocycles. The formation of spiro compounds proceeds in most cases in good yields in a one-pot reaction.Keywords: Tert-amino effect, cyclization, spiro compounds, Knoevenagel condensation, 1,2,3-thiadiazole, pyrazole, quinolineThe term tert-amino effect was coined by Meth-Cohn and Suschizky [1] to generalize cyclization reactions of certain ortho-substituted N,N-dialkylanilines. Ring closure of ortho-substituted N,Ndialkylaniline derivatives can proceed in three different ways, depending on the nature of A=B (Scheme 1). The first path (a) involves ring closure between the ortho substituted and the tert-nitrogen atom. The second path (b) comprises those reactions which involve one of the α-methylene groups attached to the atom A, ultimately leading to the formation of five membered rings. The third path (c) involved an analogous reaction of methylene groups and atom B which lead to the formation of a sixmembered ring. The first reaction of this type was reported in 1895 by Pinnow [2]. Most of the early examples of the reaction of compounds with an unsaturated ortho substituted involve groups with at least one heteroatom, such as nitroso [3], nitro [4][5], azo [6], amine [7], azomethine [8][9][10], carbonyl [11][12][13] or thiocarbonyl moieties as the ortho substituents [14].